The present invention relates to an improved cooling system for an internal combustion engine. More particularly, the present invention relates to an electronically controlled cooling apparatus which uses an electronically controlled valve to control coolant flow between the engine and a radiator, thereby maintaining the engine temperature at substantially an optimum temperature.
Operation of most of a vehicle's engine components is presently controlled by an on board computer known as an engine control module (ECM). Engine components such as electrical, fuel, air, exhaust, and other mechanical components are all equipped with sensors which supply the ECM with electrical signals. These electrical signals provide the ECM with information related to the engine components. Based on these signals received from the plurality of the sensors, the ECM makes decisions regarding the operation of the engine and provides control signals to operate the engine components. The ECM, the plurality of sensors, and the engine components therefor create a closed loop feedback system for controlling engine operation.
Conventional thermostats for controlling coolant fluid flow from the engine to a radiator to cool the coolant fluid and the engine use a wax motor which opens and closes a valve of the thermostat. Such conventional thermostats are passive devices. In other words, the wax inside the motor melts and expands as the engine coolant temperature rises above a predetermined level. This expansion of the wax causes movement of a piston which, in turn, opens a valve to permit coolant flow to the radiator.
The apparatus of the present invention advantageously provides an active engine temperature control apparatus. The thermostat is controlled by the ECM and/or other electronic controller. The ECM processes inputs from the plurality of sensors and calculates an optimum engine temperature. The ECM then generates a temperature control signal proportioned to the optimum engine temperature. The control signal informs the controller regarding the optimum designed engine temperature. The plurality of sensors detect, for example, coolant flow, coolant fluid temperature, engine temperature, mass air flow, throttle position, the RPM of the engine, etc. The controller provides an output signal to the electronic thermostat of the present invention to open and close the thermostat valve electronically and permit coolant flow to the radiator, thereby maintaining the temperature of the engine at substantially the optimum temperature calculated by the ECM. In other words, the electronically controlled cooling system of the present invention is capable at analyzing the current state of the engine using the sensor signals and then controlling how much coolant flow to send to or from the radiator to optimize engine temperature.
The apparatus of the present invention advantageously provides a more rapid control of coolant temperature than conventional passive systems. By using an electrical signal to heat the wax inside the thermostat, expansion of the wax and opening of the valve can occur very rapidly, preferably within about one second. Advantageously, the electronic controller can hold the thermostat valve partially open to control the amount of fluid permitted to flow to the radiator.
The present invention not only permits more accurate and rapid temperature control, but also advantageously permits the engine temperature to be set and controlled at a plurality of different levels depending on operating conditions of the engine. This feature advantageously improves fuel economy, reduces exhaust emissions, and improves overall engine performance.
According to one aspect of the present invention, an apparatus is provided for controlling the temperature of an engine based on a temperature control signal generated by an electronic control module of the engine. The electronic control module is coupled to a plurality of sensors configured to detect a plurality of engine component parameters and is configured to generate the temperature control signal related to an optimum engine temperature calculated using at least one output signal from at least one of the plurality of sensors. The apparatus includes a controller coupled to the electronic control module and to an engine temperature sensor. The controller generates an output signal based on the temperature control signal received from the electronic control module and on a signal proportional to the actual engine temperature received from the engine temperature sensor. The apparatus also includes an electronically actuated thermostat including a valve located within a coolant flow passageway of the engine and a motor electrically coupled to the controller. The motor is configured to open and close the valve to control flow of a coolant fluid in the coolant flow passageway in response to the output signal from the controller.
In the illustrated embodiment, the motor includes a housing filled with a temperature responsive expansion agent, and a heater located inside the housing. The heater is electrically coupled to the controller. The motor also includes a movable piston having an end located in the housing. The piston is movable from a retracted position to an extended position to open and close the valve as the heater heats the expansion agent in response to the output signal from the controller.
Also in the illustrated embodiment, the motor is also located in the coolant flow passageway of the engine adjacent the valve so that an increase in the temperature of the coolant fluid above a predetermined level causes expansion of the expansion agent in the housing to open the valve. This provides a fail safe feature to reduce the likelihood of an overheat condition should any of the electronic components fail.
The motor includes a first conductive member located on a first side of the heater and a second conductive member located on a second side of the heater. The first conductive member is electrically coupled to the controller and the second conductive member being grounded. In the illustrated embodiment, the motor includes an inner conductive sleeve and an outer conductive sleeve. The heater has a generally cylindrical body located between the inner and outer conductive sleeves, and the controller is electrically coupled to one of the inner and outer conductive sleeves.
According to another aspect of the present invention, an apparatus is provided for setting the temperature of an engine to a predetermined temperature to optimize performance of the engine. The apparatus includes a controller coupled to an engine temperature sensor. The controller generates an output signal related to the predetermined temperature and to a signal proportional to the actual engine temperature received from the engine temperature sensor. The apparatus also includes an electronically actuated thermostat having a valve located within a coolant flow passageway of the engine and a motor. The motor includes a housing filled with a temperature responsive expansion agent, and a heater located inside the housing. The heater is electrically coupled to the controller. The motor also includes a movable piston having an end located in the housing. The piston is movable from a retracted position to an extended position to open and close the valve as the heater heats the expansion agent in response to the output signal from the controller to maintain engine temperature at substantially the predetermined temperature.
Additional objects, features, and advantages of the invention will become apparent to those skilled in the art upon consideration of the following detailed description of a preferred embodiment exemplifying the best mode of carrying out the invention as presently perceived.